Battleships for the classroom, with lettered columns and numbered rows so every square has a grid reference. Find the fleet the computer has hidden, as a class or two teams taking turns, or play the computer, each side firing at the other's fleet. Tap a square or type its grid reference (B4) to fire. A small 6 by 6 grid, a medium 8 by 8 or a large 10 by 10.